1. Field of the Invention
The present invention relates to a hub assembly and, more particularly, to a hub assembly for a bicycle.
2. Description of the Related Art
A conventional hub assembly for a bicycle in accordance with the prior art shown in FIG. 8 comprises a shaft 54, a hub 50 rotatably mounted on the shaft 54, a mounting sleeve 52 secured on a first end of the hub 50, a first sprocket 55 mounted on the mounting sleeve 52 and having an inner wall provided with a plurality of oneway ratchet teeth 551, a plurality of pawl members 53 pivotally mounted on the mounting sleeve 52 and meshing with the oneway ratchet teeth 551 of the first sprocket 55, and a second sprocket 51 secured on a second end of the hub 50.
In assembly, the hub 50 is connected to a wheel (not shown) of the bicycle, the shaft 54 is connected to the rear stays (not shown) of a frame (not shown) of the bicycle, and the first sprocket 55 meshes with and is driven by a chain (not shown) which is driven by a chainwheel (not shown) which is driven by a pedal (not shown) that is pedalled by a rider. In operation, when the pedal is pedalled by the rider, the chainwheel is driven by the pedal to drive the chain which drives the first sprocket 55 to rotate forward. At this time, the pawl members 53 on the mounting sleeve 52 mesh with the oneway ratchet teeth 551 of the first sprocket 55 so that when the first sprocket 55 is rotated forward, the mounting sleeve 52 is also rotated forward to rotate the hub 50 forward so as to move the wheel forward. On the contrary, when the pedal is pedalled by the rider to move backward, the chainwheel is driven by the pedal to drive the chain which drives the first sprocket 55 to rotate backward. At this time, the pawl members 53 on the mounting sleeve 52 disengage the oneway ratchet teeth 551 of the first sprocket 55 so that when the first sprocket 55 is rotated backward, the mounting sleeve 52 together with the hub 50 is not rotated by the first sprocket 55, and the first sprocket 55 idles. Thus, when the first sprocket 55 is rotated forward (in the positive direction) relative to the shaft 54, the hub 50 is also rotated forward relative to the shaft 54 so as to move the wheel forward, while when the first sprocket 55 is rotated backward (in the reverse direction) relative to the shaft 54, the hub 50 is not driven by the first sprocket 55, and the first sprocket 55 idles. In such a manner, the bicycle is used for a normal riding.
Alternatively, the hub 50 and the wheel are turned around so that the second sprocket 51 meshes with and is driven by the chain. In operation, when the pedal is pedalled by the rider, the chainwheel is driven by the pedal to drive the chain which drives the second sprocket 51 to rotate forward so that the hub 50 is also driven by the second sprocket 51 to rotate forward. On the contrary, when the pedal is pedalled by the rider to move backward, the chainwheel is driven by the pedal to drive the chain which drives the second sprocket 51 to rotate backward so that the hub 50 is also driven by the second sprocket 51 to rotate backward. Thus, when the second sprocket 51 is rotated forward (in the positive direction) relative to the shaft 54, the hub 50 is also rotated forward relative to the shaft 54 so as to move the wheel forward, while when the second sprocket 51 is rotated backward (in the reverse direction) relative to the shaft 54, the hub 50 is also rotated backward relative to the shaft 54 so as to move the wheel backward. In such a manner, the bicycle is used for an acrobatic performance.
However, the user has to turn around the hub 50 and the wheel to switch the operation modes of the bicycle between a normal riding and an acrobatic performance so that the user cannot change the two operation modes of the bicycle easily and quickly, thereby causing inconvenience to the user when changing the two operation modes of the bicycle.